In blood gas analysis, it is important that air or other gaseous material not be allowed to contaminate the blood as these contaminates distort the results of the gas analysis. To compound this problem, most prior art syringes adapted to withdraw blood samples from donors are normally preconditioned by the addition of a heparin solution to provide an anticoagulant for the blood. The heparin solution is typically very dilute with the heparin concentration being approximately 1000 units per milliliter and the diluent being made up of alcohol, water, and other materials which can distort the gas analysis of the blood.
It is desirable in taking blood samples for gas analysis to isolate the blood from extraneous gaseous materials and from the diluent of the heparin solution while leaving the heparin itself to prevent coagulation of the blood.
Accordingly, it is an object of the present invention to provide a new and improved method of and syringe for taking blood samples which prevents contamination by extraneous gases which are inherently present in a syringe body or in the diluent of a heparin solution which is added to a syringe prior to use.